The invention relates to golf clubs, and in particular, to a mechanical locking device for attaching the shaft portion of a golf club to the golf clubhead.
The hosel portion of a golf club is the tubular shaped member which connects the head portion of the club to the shaft portion of the club. Hosels are generally all the same length, i.e., they do not vary from club to club within a set.
Golf club irons are designed with varying degrees of loft, ranging from a minimum of about 15.degree. for a number 1 iron to a maximum of about 60.degree. for a wedge type club. Golf clubs also vary in length. Golf club woods are designed with varying degrees of loft ranging from about 8.degree. to about 27.degree.. The different degrees of loft and length help to control the trajectory and distance a golf ball is hit. With reference to FIG. 1, a golf club iron includes a blade member 2 having a toe portion 4, a top ridge 6, a bottom sole portion 8 and a heel portion 10. Extending from the heel portion region of the clubhead is a hosel portion 12 adapted to receive and be retained on a shaft member (not shown). The clubhead is provided with a substantially flat surface 16, having therein a center of percussion 18, which is the spot ideally adapted to engage a golf ball at impact, and a rear surface 20 having a perimeter 22 defining a cavity 24.
One of the problems associated with the less lofted clubs is that the size of those clubs has generally been restricted by the head weight. The less lofted iron clubheads are typically the lightest weight because they will be cut to the longest overall club length and must still be within an acceptable swing weight range. These restrictions have thus far dictated that the size of the main body of the less lofted iron clubhead remain very small volumetrically. It is desirable to increase the size of the main body of the less lofted clubs in order to make them easier to hit.
It is also desirable to provide more of an impact on the actual distribution of weight within the normal golf clubhead shape or profile. The optimum weight distribution system of an iron type golf clubhead is one in which the optimum amount of weight is positioned toward the toe area of the head on the less lofted clubs and progressively shifts toward the heel area of the head on the more lofted clubs. Placement of the weight in these positions helps eliminate the average golfer's natural tendency to hit the ball to the right when using the less lofted clubs, and hit the ball to the left when using the more lofted clubs. Efforts to move or redistribute enough weight to produce a significant impact in this area have not been completely successful because there is simply not enough material or mass contained within the main body of the conventional clubhead profile which could be moved or redistributed to effectively achieve the optimum results.
One attempt at improvement in this area has been the use of hosels of varying lengths to permit redistribution of weight within the main body of the clubhead. U.S. Pat. No. 4,715,601 to Lamanna discloses the use of hosels of varying lengths to achieve a relatively constant center of percussion for the set of lofted clubs. Lamanna discloses a design for clubs in which the hosel portions of the clubs progress in length as the loft increases, with the standard or conventional length hosel on the lowest lofted club and the longest, or longer than conventional length hosel on the highest lofted club. As the clubhead weight increases from the lower lofted irons to the higher lofted irons, the weight of the hosel portion also increases. Therefore, the center of mass is maintained at a relatively constant location in relation to the blade portion of the clubhead and the planar face of the blade portion.
Thus, Lamanna discloses that the location of center of mass remains relatively constant for all of the various lofted clubs. As mentioned above, it is desirable to have a set of golf clubs in which the center of mass shifts, with the optimum amount of weight toward the toe area on the less lofted clubs shifting progressively toward the heel on the more lofted club.
Another problem associated with the golf clubs relates to the manner in which the shaft is attached to the clubhead. In the traditional golf club, the cylindrical shaft is inserted into a cylindrical bore inside the hosel and is held in place with epoxy cement. If the epoxy cement bond breaks, the shaft moves inside the hosel, and eventually separates from the hosel.